The suspension system in a vehicle comprises a plurality of spring/damper assemblies which vibrationally isolate the sprung mass of the vehicle, comprising the passenger carrying frame and body, from the unsprung mass of the vehicle, comprising the associated tire/wheel assemblies, so that the tire/wheel assemblies are free to move in accordance with the contour of the driving surface without imparting the same motion or corresponding forces to the frame and body. The spring/damper assembly comprises the combination of a suspension spring with a damper or shock absorber. The spring absorbs the kinetic energy of vibration imparted to the unsprung mass by the road surface, while the damper dissipates the energy associated with the motion of the unsprung mass relative to the sprung mass.
A variety of types of spring have typically been employed in vehicle suspension systems, including helical coil compression springs, leaf springs, torsion bars, and helical torsion springs. Leaf springs are typically used on non-steering wheels and operate on the principle of bending one or more preformed bars of spring steel. A vehicle suspension leaf spring typically supports the loading of an axle at the center of the spring.
U.S. Pat. No. 830,810, hereafter the No. '801 Patent) incorporated herein by reference, discloses a spring constructed from a single rod that as illustrated in FIGS. 1-4 herein is provided with oppositely turned helical coils f which project downward at the ends of a central portion t, the inner ends of coils f being attached to the central portion t, one coil f in front and the other coil f in rear of an axle a, the outer ends of the coils f attached to spring-arms g, each of which has one initial lateral bend h toward the central longitudinal plane of the axle a, in which plane the spring-arm g extends upward and lengthwise, one spring-arm g extending forward and the other spring-arm g extending rearward, each in accordance with an elliptical curve in the plane. The ends of these arms g are provided with eyes or bearing m that engage shackles p, connected to the body-bar c or to the body directly.
The No. '801 Patent teaches that the oppositely turned coils f are wound with the same helical pitch sense, so that relative to the central portion t of the spring oriented in a longitudinal direction, the fore and aft coils f are disposed on different lateral sides of the spring. This causes the effective width, or overall lateral extent, of the spring to be relatively wide, particularly if the spring-arms g are located within the same plane, which is a disadvantage for packaging the spring within the vehicle suspension. Moreover, this requires lateral bends in the spring to minimize the effective width of the spring which causes the spring to be weaker and more difficult to manufacture.